Subscribers to Office 365 - Microsoft’s very internet-centric, subscription-based version of its Office productivity suite - can now download a free iOS app from their iPhone’s App Store. Well, free in the sense that they’ve already paid for it as part of their annual or monthly Office 365 subscription.

For now it’s only Microsoft’s customers in the US who can download the app, though. Microsoft says that an additional 135 markets and 27 languages will get it “very soon". Hopefully we’ll get it by June 28, the second anniversary of Office 365 coming to market.

The app will let you “access, view and edit" Word, Excel and PowerPoint documents on your iPhone, according to Microsoft, similar to the way you can from a Windows Phone. Just what “access" means, apart from view or edit, isn’t clear to me from this remove. Copy, perhaps?

Microsoft promises that any formatting you do from your Apple phone will be maintained when you visit the document back on your PC or in a browser. (Office 365 has a browser client, meaning you don’t have to install the full app to use it.) The app also has a “resume" function, that lets you pick up editing a document on your phone exactly where you left editing it on your PC.

You can also save documents directly from the phone to SkyDrive, Microsoft’s take on Dropbox.

There’s no word yet on an iPad-optimised version, which is a pity because it’s the iPad on which Office 365 will be most useful. Like the rest of the world outside the US, iPad users will just have to wait and see. Or they can use that web-based version of Office 365 I mentioned earlier.